The present invention relates to a memory card comprising an erasable and programmable nonvolatile memory, for example, a flash memory and the technology which can be applied effectively to high-speed data writing operation.
Data writing to a memory card comprising a flash memory is performed after storing the writing data to a buffer from a host computer and then erasing sectors of physical address for data writing. Since the sectors are erased before the data writing, distribution of threshold voltage in the memory cell considered as the abject of data writing may be formed previously to the desirable distribution form.
However, if the operation power source is disconnected during the erasing operation or before the completion of writing operation, sector data not considered as the object of data writing may be lost in some cases. Namely, since a plurality of sectors are all considered as the object of the data writing process even if only a part of sectors is updated when data writing is performed in unit of a plurality of sectors within the flash memory, a plurality of sectors in unit of data writing are all lost due to unwanted disconnection of power source.
An example of the erasing process in the flash memory is described in the patent document 1.
[Patent Document 1]
Japanese Unexamined Patent Publication No. Hei 11(1999)-345494